Siemens Sitrans LR250 Instruction Manual page 121

The material level should be below all known obstructions at the moment when Auto
False Echo Suppression learns the echo profile. Ideally the vessel should be empty or
almost empty, and if an agitator is present, it should be running.
The device learns the echo profile over the whole measurement range and the TVT is
shaped around all echoes present at that moment.
Auto Suppression Range (2.2.4.3.)
Auto Suppression Range specifies the range within which the learned TVT is applied.
Default TVT is applied over the remainder of the range.
The learned TVT screens out the false echoes caused by obstructions. The default TVT
allows the material echo to rise above it.
Auto Suppression Range must be set to a distance shorter than the distance to the
material level when the environment was learned, to avoid the material echo being
screened out.
Example before Auto False Echo Suppression
default
TVT
Example after Auto False Echo Suppression
auto suppression
false
echo
7ML19985JF02 SITRANS LR250 (PROFIBUS PA) – INSTRUCTION MANUAL
false
echo
learned TVT
default TVT
range setting
material
level
Auto Suppression Range set to
2.1 m
material
level
echo marker
sensor reference point
High Cal. Pt.
= 0
obstruction
at 1.2 m
material
level at
2.9 m
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